The present paper analyzes the spatial composition of the Cathedral of Monreale in Norman Sicily in the twelfth century, focusing on the theme and layout of the paintings. The longitudinal church without a dome is decorated with Byzantine paintings forming a unified space. Around the apse at the east end, the vertical space overlaps with the horizontal space from the west to the east. This establishes a three-dimensional religious space. Based on the space of ancient Roman longitudinal churches, a holy space was devised with the layout of the Byzantine paintings centered on the apse.
